Fentanyl/Fluanisone - Midazolam Anaesthesia in Rabbits (Disease Investigation & Management - Treatment and Care)

Summary Information
Type of technique Health & Management / Disease Investigation & Management / Techniques:
Synonyms and Keywords --
Description An anaesthetic protocol providing surgical anaesthesia.

Anaesthetic protocol

  • Give Fentanyl/fluanisone (Hypnorm) 0.3 mL/kg intramuscularly. (B601.16.w16, J15.13.w7) 0.2 - 0.3 mL/kg. (B600.5.w5, J15.30.w2)
  • Wait 5 - 10 minutes (B601.16.w16); about 10 minutes (J15.13.w7); 10 - 20 minutes. (B600.5.w5)
  • Give intravenously or intramuscularly either
    • Midazolam 1 - 2 mg/kg (B601.16.w16, J15.13.w7) 0.5 - 2.0 mg/kg (B600.5.w5, J15.30.w2)
      • Draw up a dose of 2.0 mg/kg; initially give 0.5 - 1.0 mg/kg intravenously, with more given to effect. (B600.5.w5)
    • OR give Diazepam 1-2 mg/kg (B601.16.w16, J15.13.w7) 0.5 - 2.0 mg/kg (B600.5.w5, J15.30.w2)
    • If the benzodiazepine (midazolam or diazepam) is given intravenously, a lower dose is needed than if it is given intramuscularly; this provides a faster recovery. (B601.16.w16)
  • Give supplemental oxygen throughout the anaesthetic. (B600.5.w5, B601.16.w16)


  • For deeper anaesthesia/additional analgesia:
    • Hypnorm, about one third of the original dose intramuscularly. Or dilute hypnorm 1:10 with sterile water for injection (not saline, as small crystals may form in the solution) and give by slow intravenous injection. (B601.16.w16)
  • Prolongation of anaesthesia can be achieved by giving small doses of Hypnorm - 0.05 mL/kg intramuscularly. (J83.18.w2)

Anaesthetic reversal

  • Butorphanol 0.1 - 0.5 mg/kg or buprenorphine 0.01 - 0.05 mg/kg can be given to reverse the anaesthetic and respiratory depressive effects of fentanyl while continuing to provide analgesia. (B601.16.w16, J83.23.w2)
    • Butorphanol is a mu antagonist and provides good reversal of the effects of fentanyl, but only a limited period of analgesia (2 - 3 hours). (B601.16.w16)
    • Buprenorphine provides more limited reversal of fentanyl but 6 - 8 hours of postoperative analgesia. (B601.16.w16)
    • Give subcutaneously or intravenously. (B600.5.w5)
  • Doxapram (Dopram V, Willows Francis Veterinary), reverses the respiratory depression and partially reverses sedation. (J83.23.w2)
  • Naloxone, an opiate antagonist, reverses the sedative and respiratory depressive effects but also reverses the analgesic effect. (J83.23.w2)
  • Note: if no reversal agent is given, the sedative and analgesic effects will last for about 4 - 6 hours. (B600.5.w5)
Appropriate Use (?)
  • Hypnorm provides profound analgesia and sedation. (B601.16.w16)
  • This combination gives surgical anaesthesia and good muscle relaxation for 30 - 45 minutes. (B600.5.w5, B601.16.w16, J83.18.w2)
  • With diazepam or midazolam given 10 minutes after fentanyl/fluanisone, 20 - 40 minutes of anaesthesia (J15.30.w2)
  • Does not require endotracheal intubation and therefore keeps the oral cavity accessible. (B600.5.w5)
  • Hypnorm produces vasodilatation; venipuncture is therefore simple. (B600.5.w5, B601.16.w16, J15.30.w2)
  • For intravenous administration of diazepam use the emulsion preparation (Diazemuls). (B601.16.w16)
  • Recovery time of 1 - 4 hours. (J15.30.w2)
  • Food and water can be offered once the rabbit is in sternal recumbency. (B600.5.w5)
Complications/ Limitations / Risk
  • If a formulation of diazepam containing propylene glycol is used intravenously there is a risk (low) of thrombophlebitis developing at the injection site. (B601.16.w16)
  • Prolonged recovery time (up to three hours) if no reversal agent is used. (B601.16.w16)
  • Moderate hypoxia and hypercapnia are seen. (B601.16.w16)
    • Give supplemental oxygen throughout the anaesthetic. (B600.5.w5, B601.16.w16)
Equipment / Chemicals required and Suppliers
Expertise level / Ease of Use
  • This procedure should only be carried out by an individual with appropriate clinical training and practical experience.
Cost / Availability
  • Variable cost and availability of drugs and appropriate anaesthetic equipment.
Legal and Ethical Considerations In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (See: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).

Use of Drugs (Medication):

  • Many drugs are not registered for use in lagomorphs and care should be taken in their use, with proper regard for possible toxic effects. Consideration should be give to relevant legislation regarding the use of drugs.
  • In any country, drugs are unlikely to be specifically licensed for use in non-domestic mammals. 
    • In Europe the prescription cascade must be followed, and the client's informed consent should be obtained, whenever a drug is used which is not licensed for use in a given species. (B284.5.w5)
    • In the UK, guidelines regarding the use of drugs are set out in the Royal College of Veterinary Surgeons Guide to Professional Conduct 2000: (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Choice of Medicinal Products).
Author Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Frances Harcourt-Brown BVSc FRCVS (V.w140)
References B284.5.w5, B600.5.w5, B601.16.w16, J15.13.w7, J15.30.w2, J83.23.w2

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